Various techniques have been proposed to polish the small irregularities on a surface, for example, a metal surface
(http://www.chemicoat.co.jp/column/detail_6.html).
“Chemical polishing” is a polishing technique that soaks a metal in a polishing solution and causes the surface of the metal to be corroded by a chemical reaction of an acid or an alkali. The solution spreads into every corner of the metal and thereby enables even a microstructure which is not reachable by mechanical polishing to be processed. The chemical polishing technique is mainly suitable for polishing micro-components of complicated shapes and inner surfaces.
“Electrolytic polishing” is a polishing technique that soaks a metal in an electrolytic polishing solution and causes current to flow in the solution with the metal as the positive electrode. The metal is gradually dissolved to have the glossy or smoothened surface. This technique does not make an altered layer on the surface by processing and does not leave stain or burn. Along with the chemical polishing technique, the electrolytic polishing technique is accordingly used for precision components and the like that require a clean polishing technique.
“Mechanical polishing” is a polishing technique that uses a machine for polishing and includes various methods. The current mainstream is a rotary type that applies a polishing pad on a disk-shaped surface plate, drips a liquid polishing agent including a chemical component and fine particles on the polishing pad and rotates the surface plate to polish an object. Other polishing techniques include polishing with a horning machine to precisely polish an inner diameter of a metal object and buff polishing using a buff.
Satin finishing (http:/www.chemicoat.co.jp/knowledge/detail_169.html) is a surface treatment technique that make small irregularities on the surface of a metal and provides the rough surface finishing. Satin finishing includes glossy, semi-glossy and matte surface finishing. Satin finishing is used to provide the appropriate surface roughness and improve the appearance, and is additionally used to provide slip resistance against oily hands and pretreatment prior to coating or anode oxidation. A processing technique called “scraping” may be performed to provide small irregularities for the purpose of reducing the frictional resistance on the surface of a precision machine or the like.
Satin finishing techniques of a metal surface are mainly classified into mechanical methods and chemical methods. The mechanical methods include a wire-brushing method that polishes the surface using a wire brush, a sandblasting method that sprays fine particles onto the surface by means of the compressed air and a liquid horning method that sprays a processing solution including fine particles on a metal surface to be processed, in addition to the scraping method described above. The chemical satin finishing methods include a method employing chemical corrosion or galvanic corrosion such as etching and a surface treatment method using electroplating such as dispersal plating.
Roughness meters are generally used for measurement of the surface gloss and the surface roughness. The roughness meters include mechanical types and optical types, for example, using laser. The roughness meter provides a numerical indication of the irregularities in the unit of mm or in the unit of nm. Experienced engineers, however, often determine the surface roughness by observation of the surface gloss and glaze without using such measurement. The operations on the line proceed based on such experience. The following provides prior arts of the surface roughness measurement.
The disclosures of Patent Literatures 1 to 3 have been proposed to measure the surface roughness by profiling with a stylus or the like.
The disclosures of Patent Literatures 4 to 6 have been proposed to measure the surface roughness in a contactless manner with an imaging device.
The disclosures of Patent Literatures 7 to 10 have been proposed to measure the surface roughness in a contactless manner with laser beam.